The physiological and quantitative significance of the mitochondrial contribution to the intracellular synthesis of fatty acids and glycerolipids will be investigated. Resolution and purification of the enzymes involved in phosphatidic acid synthesis and the factors governing the synthesis of a molecule with a specific molecular architecture will be undertaken. Attempts will be made using ascites tumor cells, which have been reported to exhibit a random distribution of fatty acids in their glycerolipids, to assess the functional and physiological significance of the mitochondrial glycerol-3-P acyltransferase system. Studies on the fatty acid elongation system in beef heart mitochondria will be designed, on the one hand, to test the hypothesis that this multienzyme system is different from the beta-oxidation enzymes and on the other to confirm evidence on hand that suggests that this enzyme system is assembled as a multienzyme complex, and that the increased efficiency offered by this assemblage is essential to the mechanism of the initial condensation steps.